To keep up with the bustling pace of modern human lives, a variety of mobile devices which are readily portable and compact have also flourished. Taking the smart phone, the personal digital assistant (PDA), the tablet PC, and the notebook computer for example, it not only is equipped with all the functions a traditional communication apparatus has, but also allows users to achieve purposes such as writing documents, receiving and sending electronic mails, surfing the Internet, or using instant messaging software through the built-in operating system or application programs.
When a user browses important information of files on his or her mobile phone, the user may need to store and encrypt the on-screen contents. Some mobile phone application programs corresponding to the files (e.g., photographs) in specific formats may be available for the user to encrypt the files through the menu. However, other on-screen contents (e.g., web-pages) not in the specific format may need to be converted into certain formats and can then be encrypted.
Besides, when the user takes some private pictures or photographs of confidential documents with the camera or the mobile phone capable of taking pictures or photographs, the user often performs some encryption functions before or after the photo-shooting action in order to prevent the pictures or photographs from being browsed, copied, or even stolen by others. These encryption functions, however, frequently require complicated manual operations before the photo-shooting action or specific settings after the photo-shooting action.